Problem: Find the missing fraction.
Let's look at the multiples of each denominator and see which multiples they have in common. Denominator Multiples ${4}$ $4, 8, \underline{{12}}, 16$ ${3}$ $3, 6, 9, \underline{{12}}, 15$ The least common multiple is ${12}$. Let's use multiplication to make each fraction have a denominator of $12$. ${\dfrac{3}{4}}=\dfrac{{3} \times 3}{{4} \times 3} = {\dfrac{9}{12}}$ ${\dfrac{2}{3}}=\dfrac{{2} \times 4}{{3} \times 4} = {\dfrac{8}{12}}$ So, $\boxed{\phantom{\dfrac14}} - {\dfrac9{12}}= {\dfrac{8}{12}}$ $\dfrac{9}{12}$ $\dfrac{8}{12}$ $\boxed{\phantom{{\dfrac{17}{12}}}}$ $\boxed{{\dfrac{17}{12}}} - {\dfrac9{12}}= {\dfrac{8}{12}}$ $\dfrac{9}{12}$ $\dfrac{8}{12}$ ${\dfrac{17}{12}}$ $\boxed{{\dfrac{17}{12}}} - {\dfrac{3}{4}} = {\dfrac{2}{3}}$ ${\dfrac{17}{12}}$ can also be written as ${1 \dfrac{5}{12}}$.